Synthesis of fluorescent carbon quantum dots (CQDs) through the mild thermal treatment of agro-industrial residues assisted by γ-alumina

  • Paola BrachiEmail author
Original Article


Carbon deposits are well known to cover the γ-alumina surface when exposed to high temperatures in the presence of carbonaceous feedstocks by means of coking and/or fouling mechanisms. Herein, it is demonstrated that this phenomenon, which is extremely undesirable when γ-alumina is used as a catalyst or an adsorbent material, can be successfully exploited for the production of fluorescent carbon-based quantum nanodots (CQDs) under mild conditions of temperatures (250–300 °C) and time (30 min) by using residual biomasses as a carbon source. Specifically, four agro-industrial residues including sugar beet pulp (SBP), grape marc, tomato peels and seeds, and olive pomace have been successfully tested for the synthesis of biomass-based CQDs. Different techniques including UV–vis spectroscopy, fluorescence spectroscopy (PL), X-ray photoelectron spectroscopy, Raman spectroscopy, and transmission electron microscopy (TEM) have been applied for the characterization of the as-prepared SBP-based CQDs. Results highlight that the obtained carbon dots exhibit excellent solubility in both water and organic media. In addition, TEM investigations show that such nanoparticles disclose a rather uniform spherical morphology and a narrow size distribution in the range of 2–4 nm. The typical excitation dependent PL emission behavior of carbon-based quantum dots was also observed by PL analysis. Unlike other currently available bottom-up synthesis routes, a high-value by-product is obtained during the synthesis of biomass-based CQDs assisted by γ-Al2O3, i.e., the residual thermally treated biomass, which can be further valorized as a high-quality solid biofuel exhibiting a lower oxygen-to-carbon ratio and, hence, a higher calorific value than the parent biomass. The innovative finding of the present work is that a catalyst can be used to produce CQDs from the volatile matter that is driven off the biomass by heating, which opens up new possibilities of valorization for the off-gas substream coming from other biomass conversion process, like for example slow pyrolysis and carbonization.

Graphical abstract


Biomass-based carbon dots γ-Alumina catalyst Agro-industrial residues Dry thermal synthesis Fixed-bed reactor 



The author is grateful to Professor Giuliana Gorrasi (University of Salerno) for providing expertise and access to UV–visible spectrophotometer.


  1. 1.
    Wang R, Lu KQ, Tang ZR, Xu YJ (2017) Recent progress in carbon quantum dots: synthesis, properties and applications in photocatalysis. J Mater Chem A 5:3717–3734. CrossRefGoogle Scholar
  2. 2.
    Zhang J, Yu SH (2016) Carbon dots: large-scale synthesis, sensing and bioimaging. Mater Today Chem 19:382–393. CrossRefGoogle Scholar
  3. 3.
    Himaja AL, Karthik PS, Singh SP (2015) Carbon dots: the newest member of the carbon nanomaterials family. Chem Rec 15:595–615. CrossRefGoogle Scholar
  4. 4.
    Yang F, LeCroy GE, Wang P, Liang W, Chen J, Shiral Fernando KA, Bunker CE, Qian H, Sun YP (2016) Functionalization of carbon nanoparticles and defunctionalization—toward structural and mechanistic elucidation of carbon “quantum” dots. J Phys Chem C 120:25604–25611. CrossRefGoogle Scholar
  5. 5.
    Sukhanova A, Nabiev I (2008) Fluorescent nanocrystal quantum dots as medical diagnostic tools. Expert Opin Med Diagn 4:429–447. CrossRefGoogle Scholar
  6. 6.
    Yang S, Cao L, Luo P, Lu F, Wang X, Wang H, Meziani MJ, Liu Y, Qi G, Sun YP (2009) Carbon dots for optical imaging in vivo. J Am Chem Soc 131:11308–11309. CrossRefGoogle Scholar
  7. 7.
    Bui TT, Park SY (2016) A carbon dot–hemoglobin complex-based biosensor for cholesterol detection. Green Chem 18:4245–4253. CrossRefGoogle Scholar
  8. 8.
    Wang QL, Huang XX, Long YJ, Wang XL, Zhang HJ, Zhu R, Liang L, Teng P, Zheng H (2013) Hollow luminescent carbon dots for drug delivery. Carbon 59:192–199. CrossRefGoogle Scholar
  9. 9.
    Zhu H, Wang X, Li Y, Wang Z, Yang F, Yang X (2009) Microwave synthesis of fluorescent carbon nanoparticles with electrochemiluminescence properties. Chem Commun 34:5118–5120. CrossRefGoogle Scholar
  10. 10.
    Hutton GAM, Martindale BCM, Reisner E (2017) Carbon dots as photosensitisers for solar-driven catalysis. Chem Soc Rev 46:6111–6123. CrossRefGoogle Scholar
  11. 11.
    Briscoe J, Marinovic A, Sevilla M, Dunn S, Titirici M (2015) Biomass-derived carbon quantum dot sensitizers for solid-state nanostructured solar cells. Angew Chem Int Ed 54:4463–4468. CrossRefGoogle Scholar
  12. 12.
    Chen QL, Wang CF, Chen S (2013) One-step synthesis of yellow-emitting carbogenic dots toward white light-emitting diodes. Mater Sci 48:2352–2357. CrossRefGoogle Scholar
  13. 13.
    Devadas B, Imae T (2018) Effect of carbon dots on conducting polymers for energy storage applications. ACS Sustain Chem Eng 6:127–134. CrossRefGoogle Scholar
  14. 14.
    Xu X, Ray R, Gu Y, Ploehn HJ, Gearheart L, Raker K, Scrivens WA (2004) Electrophoretic analysis and purification of fluorescent single-walled carbon nanotube fragments. J Am Chem Soc 126:12736–12737. CrossRefGoogle Scholar
  15. 15.
    Jelinek R (2017) Carbon-dot synthesis. In: Jelinek R (ed) Carbon quantum dots—synthesis, properties and applications. Springer, Cham. CrossRefGoogle Scholar
  16. 16.
    Sun YP, Zhou B, Lin Y, Wang W, Shiral Fernando KA, Pathak P, Meziani MJ, Harruff BA, Wang X, Wang H, Luo PG, Yang H, Kose ME, Chen B, Veca LM, Xie SY (2006) Quantum-sized carbon dots for bright and colorful photoluminescence. J Am Chem Soc 28:7756–7757. CrossRefGoogle Scholar
  17. 17.
    Namdari P, Negahdari B, Eatemadi A (2017) Synthesis, properties and biomedical applications of carbon-based quantum dots: an updated review. Biomed Pharmacother 87:209–222. CrossRefGoogle Scholar
  18. 18.
    Das R, Bandyopadhyay R, Pramanik P (2018) Carbon quantum dots from natural resource: a review. Mater Today Chem 8:96–109. CrossRefGoogle Scholar
  19. 19.
    Sharma V, Tiwari P, Mobin SM (2017) Sustainable carbon-dots: recent advances in green carbon dots for sensing and bioimaging. J Mater Chem B 5:8904–8924. CrossRefGoogle Scholar
  20. 20.
    Prasannan A, Imae T (2013) One-pot synthesis of fluorescent carbon dots from orange waste peels. Ind Eng Chem Res 52:15673–15678. CrossRefGoogle Scholar
  21. 21.
    Devaraju MK, Honma I (2012) Hydrothermal and solvothermal process towards development of LiMPO4 (M = Fe, Mn) nanomaterials for lithium-ion batteries. Adv Energy Mater 2:284–297. CrossRefGoogle Scholar
  22. 22.
    Wang D, Wang Z, Zhan Q, Pu Y, Wang JX, Foster NR, Dai L (2017a) Facile and scalable preparation of fluorescent carbon dots for multifunctional applications. Engineering 3:402–408. CrossRefGoogle Scholar
  23. 23.
    Yuan T, Meng T, He P, Shi YX, Li Y, Li X, Fan L, Yang S (2019) Carbon quantum dots: an emerging material for optoelectronic applications. J Mater Chem C 7:6820–6835. CrossRefGoogle Scholar
  24. 24.
    Argyle MD, Bartholomew CH (2015) Heterogeneous catalyst deactivation and regeneration: a review. Catalysts 5:145–269. CrossRefGoogle Scholar
  25. 25.
    Prokudina NA, Paukshtis EA, Buyanov RA, Chesnokov TA, Konovalova VV (1996) Role of carbonate-carboxylate species during alumina coking. React Kinet Catal Lett 59:187–192. CrossRefGoogle Scholar
  26. 26.
    Rezaei PS, Shafaghat H, Daud WMAW (2014) Production of green aromatics and olefins by catalytic cracking of oxygenate compounds derived from biomass pyrolysis: a review. Appl Catal A 469:490–511. CrossRefGoogle Scholar
  27. 27.
    Kim HH, Lee YJ, Park C, Yu S, Won SO, Seo WS, Park C, Choi WK (2018) Bottom-up synthesis of carbon quantum dots with high performance photo- and electroluminescence. Part Part Syst Charact 1800080. CrossRefGoogle Scholar
  28. 28.
    Tian H, Shen HX, Qiao L, Zheng W (2018) N, S co-doped graphene quantum dots graphene–TiO2 nanotubes composite with enhanced photocatalytic activity. J Alloys Compd 691:369–377. CrossRefGoogle Scholar
  29. 29.
    Kharangarh R, Umapathy S, Singh G (2018) Thermal effect of sulfur doping for luminescent graphene quantum dots. ECS J Solid State Sci Technol 7:M29–M34. CrossRefGoogle Scholar
  30. 30.
    Hodkiewicz J (2010) Characterizing graphene with Raman spectroscopy. Thermo Sci Appl Note 51946 Accessed 22 Mar 2019
  31. 31.
    Choi Y, Jo S, Chae A, Kim YK, Park JE, Lim SY, Park D (2018) Simple microwave-assisted synthesis of amphiphilic carbon quantum dots from A3/B2 polyamidation monomer set. ACS Appl Mater Interfaces 9:27883–27893. CrossRefGoogle Scholar
  32. 32.
    Liu X, Hao J, Liu J, Tao H (2018) Green synthesis of carbon quantum dots from lignite coal and the application in Fe3+ detection. IOP Conf Ser Earth Environ Sci 113:012063. CrossRefGoogle Scholar
  33. 33.
    Divya S, Narayan S, Ainavarapu RK, Khushalani D (2019) Insight into the excitation-dependent fluorescence of carbon dots. Chem Phys Chem 20:984–990. CrossRefGoogle Scholar
  34. 34.
    Huang C, Dong H, Su Y, Wu Y, Narron R, Yong Q (2019) Synthesis of carbon quantum dot nanoparticles derived from byproducts in bio-refinery process for cell imaging and in vivo bioimaging. Nanomaterials 9:387. CrossRefGoogle Scholar
  35. 35.
    Wang H, Sun C, Chen X, Zhang Y, Colvin VL, Seo QRJ, Feng S, Wang S, Yu WW (2017b) Excitation wavelength independent visible color emission of carbon dots. Nanoscale 9:1909–1915. CrossRefGoogle Scholar
  36. 36.
    Wu M, Zhan J, Geng B, He P, Wu K, Wang L, Xu G, Li Z, Yin L, Pan D (2017) Scalable synthesis of organic-soluble carbon quantum dots: superior optical properties in solvents, solids, and LEDs. Nanoscale 9:13195–13202. CrossRefGoogle Scholar
  37. 37.
    Zhou Y, Mintz KJ, Oztan CY, Hettiarachchi SD, Peng Z, Seven ES, Liyanage PY, De La Torre S, Celik E, Leblanc RM (2018) Embedding carbon dots in superabsorbent polymers for additive manufacturing. Polymers 10:1–12. CrossRefGoogle Scholar
  38. 38.
    Khan S, Gupta A, Verma NC, Nandi CK (2017) Time-resolved emission reveals ensemble of emissive states as the origin of multicolor fluorescence in carbon dots. Nano Lett 15:8300–8305. CrossRefGoogle Scholar
  39. 39.
    Nhuchhen DR, Afzal MT (2017) HHV predicting correlations for Torrefied biomass using proximate and ultimate analyses. Bioengineering 4:2–15. CrossRefGoogle Scholar
  40. 40.
    Brachi P, Miccio F, Miccio M, Ruoppolo G (2016) Torrefaction of tomato peel residues in a fluidized bed of inert particles and a fixed-bed reactor. Energy Fuel 30:4858–4868. CrossRefGoogle Scholar
  41. 41.
    Brachi P, Riianova E, Miccio M, Miccio F, Ruoppolo G, Chirone R (2017) Valorization of sugar beet pulp via Torrefaction with a focus on the effect of the preliminary extraction of pectins. Energy Fuel 31:9595–9604. CrossRefGoogle Scholar
  42. 42.
    Kumar A, Jones DD, Hanna MA (2009) Thermochemical biomass gasification: a review of the current status of the technology. Energies 2:556–581. CrossRefGoogle Scholar
  43. 43.
    Eberly PE, Kimberlin CN, Miller WM, Drushel HV (1996) Coke formation on silica–alumina cracking catalysts. Ind Eng Chem Process Des Dev 5:193–198. CrossRefGoogle Scholar
  44. 44.
    Guisnet M, Magnoux P (2001) Organic chemistry of coke formation. Appl Catal A 212:83–96. CrossRefGoogle Scholar
  45. 45.
    Brachi P, Chirone R, Miccio F, Miccio M, Picarelli A, Ruoppolo G (2014) Fluidized bed co-gasification of biomass and polymeric wastes for a flexible end-use of the syngas: focus on bio-methanol. Fuel 128:88–98. CrossRefGoogle Scholar

Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019
corrected publication 2019

Authors and Affiliations

  1. 1.Institute for Research on Combustion, National Research CouncilNaplesItaly

Personalised recommendations